.banner {
    position: relative;
    top: 0px;
    left: 0px;
    height: 350px;
    width: 100%;
    background: #f1f1f1;
    background: radial-gradient( at center, #f1f1f1, #f1f1f1);
}

#particles-js {
    background-size: cover;
    background-position: 50% 50%;
    background-repeat: no-repeat;
    width: 100%;
    height: 200px;
    position: absolute;
    top: 50px;
    left: 0;
    z-index: 0;
}